Electronic tube



Nov. 23, 1948. I H. A. ZAHL ETAL I 2,454,293

ELECTRONIC TUBE Filed July 29, 1945 2 Sheets-Sheet l INVENTOR HAROLD AZAHL GLENN F. ROUSE 7 JOHN G/oRHAM Patented Nov. 23, 1948 ELECTRONICTUBE Harold A. Zahl and Glenn F. Rouse, Long Branch, and John E. Gotham,Spring Lake, N. J.

Application July 29, 1943, Serial No. 496,654

4 Claims.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3'700. G. 757) The invention described herein may be manufactured and usedby or for the Government for governmental purposes, without the paymentto us of any royalty thereon.

This invention relates to improvements in electronic tubes, and moreparticularly to improvements in oscillator tubes for the generation ofultrahigh frequency energy.

A number of difficulties arise with high-power oscillator tubes workingat ultrahigh frequency. It is difficult to obtain enough cathode areafor adequate electron emission. There is a sharp break in the tunedfilament circuit (with respect to radio frequency energy) between therelatively thin wire leads of the cathode and the more massive externalpart of the filament-tuning circuit.

One particular oscillator tube which is efilcient and desirable in manyrespects is the tube disclosed and claimed in a copending application ofHarold A. Zahl, Serial No. 473,556, filed January 25, 1943. This tuberaises a difficulty because, in order to obtain adequate cathodeemission, four electrode assemblies or so-called barrels have beenemployed, instead of two. The four filaments require four pairs ofleads, and four glass stems to seal the leads, all of these stems beinglocated relatively close together, thus making the tube a difficultglass-blowing job and assembly job.

One object of the present invention is to generally improve electronemission tubes. Another object of the present invention is to overcomethe difficulties and disadvantages pointed out above. Another object ofour invention is to obtain maximum cathode emission with minimum powerconsumption for cathode heating. Another object of our invention is toprovide a cathode-tuning circuit which is very efiicient for radiofrequency oscillation. Still another object of our invention is toprovide an efiicient tube of simplified construction.

To accomplish the foregoing objects and other objects, some of whichhereinafter appear, our invention resides in the electron tube elementsand their relation one to the other as are hereinafter more particularlydescribed in the following specification. The specification. isaccompanied by drawings in which: s

Figure 1 is a front elevation of an electronic tube embodying featuresof our invention;

Figure 2 is an end elevation of the same;

Figure 3 is a longitudinal section through a cathode unit made inaccordance with our invention;

Figure 4 is a longitudinal section through the anode lead of the tube;

Figure 5 is a schematic diagram explanatory of a feature of the tube;

Figure 6 is a modification thereof;

Figure 7 is a diagram schematically showing the external tuned circuitsof the tube;

Figure 8 is a plan view of the anode structure of the tube;

Figure 9 is a front elevation of the same;

Figure 10 is an end elevation of the same;

Figure 11 shows a detail of the anode structure;

Figure 12 is a plan view of the grid structure;

Figure 13 is a front elevation of the same;

Figure 14 is a transverse section taken approximately in the plane ofthe line l4-l4 of Figure 12; and

Figure 15 is a section taken approximately in the plane of the linel5-l5 of Figure 3, and is explanatory of a step in the fabrication ofthe cathode unit.

Referring to the drawing, and more particularly to Figures 1 and 2, theparticular tube there shown comprises spaced anodes l2, connected byanode-to-anode circuits or loops l4. Grids I6 are disposed within theanodes l2 and are connected by tuned grid circuits or loops l8. Cathodes(not visible in Figures 1 and 2) are disposed within the grids I6 andare carried at the upper ends of tubular cathode leads 20. The anodesare supported by anode leads 22, and the grid circuits are supDQrted byleads 24.

The operation of this particular tube may be explained with reference toschematic Figures 5, 6 and 7. Figure 5 shows how the anodes I2 areconnected by a preferably U-shaped resonant anode circuit I4, while thegrids [6 are connected by a second preferably U-shaped resonant circuit[8. The cathodes are indicated at 26. Referring now to Figure 6, it willbe seen that the circuit is' substantially the same, except that twotuned grid and anode loops have been provided on opposite sides of thegrids and anodes. It will be understood that the oppositely-directedanode circuits l4 correspond to the structural parts [4 shown in Figures1 and 2, and that the oppositelydirected grid circuits [8 correspond tothe structural parts l8 shown in, Figures 1 and 2.

The external wiring is schematically shown in Figure '7. For the sake ofclarity this is based on the simplified showing of Figure 5. In Figure7, it will be seen that external anode leads 22 are shorted by anadjustable shorting bar 28. The anodes may be operated at either groundpotential or at a high positive potential (with restem or other suitablemetal.

'spect to direct current) and this is applied by means of a lead 3B. Thecathode leads 2!] are tuned by means of an adjustable shorting :bar 322,and the cathodes may be connected either to ground or to a source ofhigh negative potential (with respect to direct current). In the presentcase they are grounded at 3d. An appropriate grid biasing potential maybe applied to the grids through another connection 24.

The power output from the tube may be taken from either the anodecircuit or the cathode circuit. This may be done by means of anappropriate transmission line, but in the present case the output isschematically shown as being delivered directly to the poles of anantenna 38.

The features of the present invention relating to the cathode unit maybe described with reference to Figure 3 of the drawing, in which t ecathode 26 is a cylinder made of a. suitable cathode metal (for example,sheet nickel) and is secured in coaxial relationto a tube 38 made of asuitable lead-in metal (for example, Kovar).

' The cathode cylinder is closed at the top by means of a flanged disl;or cap dfi. Tube SS preferably has a diameter approaching that of thecathode,

and in the specific unit illustrated the structure appears to be onecontinuous element, the difference in thickness for the cathode beingvery slight, alt ough exaggerated in the drawing for the sake ofclarity. The coaxial relation of the cathode and cathode lead is verydesirable for eiiicient conduction of high radio frequency energy, andconstitutes one of the main advantages of thepresent improved cathodeunit.

' The heating filament 32 may be made of tung- To energize the filament,a pair of leads may be used within'the tubetEb-ut we prefer to connectthe upper end of the filament to the disk'fillas shown, sothat --thecircuit may be completed by the addition of a single wire i i runningthrough tube 38. This wire is supported near its lower-end-bymeans of aninsulation orglass bead Ma. 'The wire 44 and glass bead are preferablysubstantial in dimension so that-the wire will require no furthersupport to'keep-it in the-desired preferably coaxial position. The lowerend'of filamentfiz-is 1 connected to the upper end of wire i i bymeansof a small metallic connector'tfl.

This is-generally cylindrical andprovided'with a small'hole at the topto receive the lower end of the filament, and a large hole at the bottomto receive the top end of --wire 44.

To-assem'ble the parts of the tuba-the upper end of thefilament-iswelded to disk-Ml before disk idis welded to cylinder ZB. The lower endof filament d2 iswelded to connector d8 before cylinder "2% is securedto tube 38. secured within tube 33 by means of glass bead 46 before thecathode assembly is secured to the The wire 44 is lead 38. Thetwoassemblies are then put'together, the-lower end of the cathodecylinder26 icing welded to the upper end of tube-3B. Diametricallyopposed holes-i! are provided near the upper end of tube 38, and byworking through these holeathe operator makes sure that connector i8 isin proper position on wire 4d, followof the main envelope.

tate sealing to the glass envelope.

An important benefit of the cylindrical cathode i its large area, thusmaking possible substantial electron emission. However, to heat a largendrical cathode instead of a thin filament raises considerabledifilculty. We have found that it is feasible to use an oxide coatingfor the cathode even though the cathode is used in a relatively powerfuloscillator for transmission When using an oxide coating, the cathodewill operate at relatively low temperature and the cathode may thereforebe suficiently heated without difilculty by means of a simple internalheater filament, as above described. An appropriate coating of barium orstrontium carbonate or a combination of these compounds is applied tothe cathode surface, from which the desired oxide coating is laterformed while the tube is on the pump. The carbonate coating mayconveniently be applied after completion of the structure of the cathodeunit,

The anode structureis illustrated-in Figures 9. and 10 of the drawing.The anodes are sheet anodes are secured. on opposite sides of the anodecircuits or loops. More specifically, the loops are made of channels 58and 60,'closed at the ends by U-shap-ed pieces 62. The inwardly-turnedflanges (i i of the channels-are cut away at the center as indicated at66, thus facilitating bending of the-metal to conform to the cylindricalanodes 58. Top and bottom plates 68 and 10 may be secured toitheanodes,and have their inwardly-directed "ends overlaying the channels Theanodes maybe completed by cooling fins 'M, which in the present case aretroughshaped pieoesof metal having bent-over ends. The backs of thetroughs are secured to the outside of the cylinders 56,while the endsare secured to the top and bottomplatesfit and H1. vIt will beunderstood that all of thelparts of thestructure are secured together bywelding'or other appropriate method.

Reverting to Figures 1 and 2, the anode structure is supported by theanode leads 22, which extend-upwardly throughthe glass envelope of thetube. The-leads=22 are connected to the anode structure by means ofyoke-shaped pieces yoke isprovidedwith an internal-threaded boss 8!],the'lower end of which is slit to straddle the yoke ldand is securedthereto, as by means of a pin 82 which is preferably welded in position.

The anode lead itself is shown in Figure l, in which it will be seenthat the lower part 84. is solid and is threaded at85 to mate with thethreaded hole 88 of the yoke (Figures'lO and 11). The upper part' ll(Figure 4). of the anode lead is tubular and is preferably made of Kovarto-facili- The solid part 84 and the tube 90 are secured together, as bymeans of welding or the use of a pin 92, or both. The upper'end of tube90'is sealed'by' a plug'94, which may be welded in position.

The grid structureis-shown in'Figures 12, 13 and 14 of the drawing.Thegridsare made of vertical wires H10, the lower ends of Whicharewelded on the outside of a short tube or mandrel I02. The wires arepreferably in pairs, that is, relatively long wires are reversely bentat the top, and the open lower ends are secured to the mandrel. Theupper ends may be bent inwardly to partially close the upper end of thegrid, as is best shown at I04 in Figure 12. The resulting wire cage maybe reenforced by circular wires I06.

The grid circuit structure is made of metal channels I08 and III),closed at the ends by U-shaped pieces II2. Sheet metal ears H4 are addedat the ends to receive the support wires 24 (Figures 1 and 2), whichpass through the glass envelope of the tube.

The grids are secured to the grid circuits by pieces of sheet metal I I6(Figure 12), which are bent around the mandrels I02. The ends of thepieces H6 are turned outwardly and are secured directly to the outsideof the channels I08, IIO. It will be understood that the supports IIGare so dimensioned as to locate the grids coaxially within the anodes.

Reverting to Figures 1 and 2, it will be seen that the glass envelopeI20 is generally cylindrical, with the tuned circuits I4 and I8 disposedlongitudinally thereof. The envelope is exhausted through a tubulationI22. The grid leads 24 pass through downwardly-projecting glass stemsI24. These are spaced widely apart and are far from the other stems ofthe tube. The anode leads 22 pass through upwardly-directed glass stemsI26. These are remote from the other stems, thus facilitating theglass-blowing operation, and insuring against breakdown under highvoltage. The cathode leads 20 pass downwardly through glass stems I28.These are remote from the other stems, and are far more convenient tomake than is the case with the four-barrel tube of the patentapplication, Serial Number 473,556, aforesaid, in which four independentglass stems are located in closely adjacent relation.

It may be helpful to set forth the specific dimensions of a few tubesmade in accordance with the present invention. These tubes were designedto oscillate at about 600 me. In the case of the particular tubeillustrated, the cathode was made of 0.005" thickness nickel and had adiameter of 0.395". The overall length of the cathode was 1%". Theeffective or oxide-coated length of the cathode Was 1". The cathode canwas mounted on a seamless nickel-plated Kovar tube, having a diameter of0.375".

The sides of the grid loop were made of 0.010" channeled tantalum, thevertical inside width of the channel being A. The ends were closed byU-shaped pieces of tantalum having a thickness of 40 mil. The length ofthe grid loop was 4" inside, and the width of the grid loop or spacingbetween its sides was inside. The inside diameter of the grid cage was0.528". The length of the grid cage was 1%". The cage was made of 20equally-spaced wires, the wires being 12 mil 6 ode was 1", and thespacing between centers of the two anodes was 1%".

In another example having a larger barrel, the cathode was made of0.005" thickness nickel formed on a mandrel having a diameter of 0.515".The overall length of the cathode was 1%. The effective or oxide-coatedlength of the cathode was 1". The cathode can was mounted on a seamlessKovar tube, having a diameter of The grid loop was dimensioned asbefore. The diameter of the grid cage was 0.635" 0. d. and 0.611" 1. d.The overall length of the grid cage was 1%". The cage was made of 32equallyspaced wires, the wires being 12 mil platinumclad molybdenum. Thegrid was made on a copper mandrel having a diameter of 0.629".

The anode loop was dimensioned as before. The anode tubes were made of0.020" tantalum having an inside diameter of 0.794". The length of theanode was 1" and the spacing between centers of the two anodes was 1%,".

In still another tube, the cathode diameter was increased still furtherfrom 0.515" to 0.652". In both of these cathode units, the Kovar cathodelead was kept at a diameter of only thus necessitating an inward step(preferably sloping or frustro conical) between the cathode can and theKovar lead. This was done mainly because seamless Kovar tubing is not atpresent available in sizes larger than and we encountered difliculty inmaintaining proper vacuum when using seamed instead of seamless Kovartubing. Moreover, there is greater difiiculty in sealing a glass stem toa lead when the diameter is too great. It should be noted, however, thateven with a reduction in diameter between the cathode and the tubularlead, there still remain the important advantages that the lead issymmetrically and coaxially related to the oathode, and that the lead isa large-diameter, efficient conductor for ultrahigh frequency energy.

It will be understood that the foregoing specific dimensions are givensolely by way of exemplification, and not in limitation of theinvention.

It is believed that the construction and assembly of our new electronictube, as well as the advantages thereof, will be apparent from theforegoing detailed description. It will also be understood that our newcathode unit is of value for use in tubes different from that heredisclosed, although it is of particular value for the present tube.

It will be apparent that while we have shown and described our inventionin a preferred form, changes and modifications may be made in thestructure disclosed without departing from the spirit of the inventionas sought to be defined in the following claims.

We claim:

1. An oscillator tube for generating ultrahigh frequencies, said tubecomprising an elongated envelope, an approximately elliptical circuitdisposed inside the envelope in the direction of the axis of theenvelope, a second approximately elliptical circuit disposed generalyparallel to the first, anodes secured directly on the outside of eachside of said first circuit, a grid disposed within each anode, the endsof said grids projectin-g beyond the ends of said anodes and beingsecured directly to the sides of said second circuit, cathodes insidesaid grids, each cathode including a cylindrical can having a heatingfilament therein, tubular cathode leads extending from the cathodestransversely of the enveloped axis through the side wall of theenvelope, additional 7 filament-heating leads running through saidtubular cathode leads, grid-leads extending through .the envelope, andanode leads extending from the 'the envelope in the direction-of theaxisof the envelope, a second approximately elliptical cirouit disposedgenerally parallel tothe firstlin revgeneratively-coupled relationthereto, anodes secured'directlyon the outside ofeach'side-of said firstcircuit, a grid disposed within each anode,

the ends of said grids projecting beyond the ends of said anodes andbeingsecured directly to the sides of said second circ'uin cathodesinside'said grids, each cathode including an oxide-coated cylindricalcan having a heating filament therein, tubular cathode leads extendingfrom the cathodes transversely of the envelope axis through the sidewallof the envelopasaid tubular cathode leads having a diametersubstantially equal to that of the cathode cans, additionalfilament-heating leadsrunning through-said tubular cathode leads, gridleads extending from the remote ends of the grid circuit through theenvelope, and tubular anodeleads extending from the anodes through theenvelope in a'direction transverse to the envelope axis.

3. A cathode structure comprising a tubular member, a heating filamentat one end-of said member, a filament lead extending from the other endof said member to a point therein in the Vicinity of said filament, saidmember-havingian aperture at said point 'to permit entry of a tool forfastening said filament to said lead.

4-. A cathode structure comprising a tubular member, a'heating filamentat one end of said member, one end of said filament being co ected tosaid member, the other end of said fi ament having a connector weldedthereto, a fil ment lead'extending from the other end of said ember to-apoint therein in the vicinity of said connector, said member having anaperture at said point to permit entry of a tool for fastening saidconnector to said lead.

HAROLD A. ZAHL. GLENN F. ROUSE. JOHN E. GORHAM.

REFERENCES CITED The followingreferences are'of record in the rfile ofthis patent:

UNITED STATES PATENTS Number Name Date 1,650,232 Pickard Nov. 22, 19271,877,708 West Sept. 13, 1932 1,886,705 Lucian Nov. 8, 1932 1,924,319Hull Aug. 29, 1933 1,997,019 Schloemilch Apr. 9, 1985 2,006,904 Runge etal July 2, 1935 2,057,170 Usselman Oct. 13, 1936 2,108,640 Bieling Feb.15, 1938 2,224,649 Harris Dec. 10, 1940 2,239,303 'Purrington Apr. 22,1941 2,367,332 Bondley Jan. 16, 1945 FOREEGN PATENTS Number Country Date601,155 France Nov. 26, 1925 Certificate of Correction Patent No.2,454,298. November 23, 1948. HAROLD A. ZAHL ET AL.

It is hereby certified that errors appear in the printed specificationof the above numbered patent requiring correction as follows:

Column 5, line 50, for 1%" read 1% column 6, line 74, claim 1, forenveloped read envelope;

and that the said Letters Patent should be read with these correctionstherein that the same may conform to the record of the case in thePatent Office.

Signed and sealed this 19th day of April, A. D. 1949.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

